Field of the Invention
The present invention relates to mobile communication.
Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) evolved from a universal mobile telecommunications system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink.
Such LTE may be divided into a frequency division duplex (FDD) type and a time division duplex (TDD) type.
As set forth in 3GPP TS 36.211 V10.4.0, the physical channels in 3GPP LTE may be classified into data channels such as PDSCH (physical downlink shared channel) and PUSCH (physical uplink shared channel) and control channels such as PDCCH (physical downlink control channel), PCFICH (physical control format indicator channel), PHICH (physical hybrid-ARQ indicator channel) and PUCCH (physical uplink control channel).
Meanwhile, recently, a technique called a Cooperative Multi-point transmission/reception (CoMP) is introduced. According to the CoMP technique, a user equipment (UE) may receive data from a plurality of transmission points (TPs) simultaneously. Here, the transmission point may be a base station or a Remote Radio Head (RRH).
Generally, since an RRH uses the same cell ID with a base station, a cell-specific reference signal (CRS) generated based on a cell ID also becomes the same between an RRH and a base station, and thus, the RRH does not transmit the CRS.
However, the fact that the RRH does not transmit the CRS does not matter at all on the basis of a serving cell of a UE, but matters on the basis of a neighbor cell that exerts interference on the UE. The reason is that a UE is unable to accurately measure the RSRP for an RRH of the neighbor cell, since the RRH operates in the CoMP in the neighbor cell does not transmit the CRS.